In recent years, imaging apparatuses have drawn attention to their ability to pickup information from overall sample to cell tissues as electronic images and display the images on a monitor.
For example, Japanese Translation of PCT International Application Publication No. 2008-510201 discusses a method of forming an image of a sample as a whole by connecting images of the sample that are captured at high resolution and high magnification. However, the method involves many times of image capturing to obtain an overall image of one sample, so that it is time-consuming. Japanese Patent Application Laid-Open No. 2009-003016 and Japanese Patent Application Laid-Open No. 2009-063665 each discuss a method of forming an image of a sample by capturing images of the sample at high speed and high magnification by an objective lens having a large field range and high resolution and a plurality of image sensors.
FIGS. 2A and 2B illustrate an example using a plurality of image sensors: FIG. 2A illustrates an object to be imaged; and FIG. 2B illustrates an imaging unit of an imaging apparatus. In FIG. 2A, a sample 225 as the object to be imaged is placed on a sample holding unit 220 (e.g., glass slide) within an illuminated area 228. In FIG. 2B, an image of the illumination area 228 is formed within an image-forming area 228c, and an image 225C of the object to be imaged lies on an electric substrate 420 having image sensors 430. As illustrated in FIG. 2A, light illuminates the sample (within the illumination area 228), so that an image of the sample is formed on the electric substrate 420 having the plurality of image sensors 430 (within the illumination area 228c).
It is difficult to arrange the plurality of image sensors 430 without space therebetween because of wiring, so that there is space between the image sensors. Thus, the sample or the imaging unit is driven to be displaced a plurality of times, so that an image of the sample is captured at every displaced position. The plurality of the captured image is combined to form an overall image to acquire the outer profile information of the entire sample. In this acquisition, a plurality of image sensors is used because it is extremely difficult to prepare image sensor large enough to be capable of capturing an image of a large area collectively.
In the case where a plurality of image sensors is used, when a sample is illuminated entirely and symmetrically along an optical axis as illustrates in FIG. 2A, an image is formed on an image plane as illustrated in FIG. 2B, the image extending between and outside of the image sensors. The light used to form the image parts between and outside of the image sensors is reflected by the electric substrate and machine units outside of the substrate, and hits the other electric substrates, machine units, and lenses of the imaging optical system. Consequently, the light may enter the image sensors as undesirable light such as flare for the image capturing, which may lead to degradation of image quality.
The light illuminated between and outside of the image sensors, if not reflected, is absorbed into the electric substrate as heat. The image sensors have properties that vary depending on heat, and thereby the heat may degrade the image quality.